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 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.swing.text;

import java.util.Enumeration;

/**
 * A collection of unique attributes.  This is a read-only,
 * immutable interface.  An attribute is basically a key and
 * a value assigned to the key.  The collection may represent
 * something like a style run, a logical style, etc.  These
 * are generally used to describe features that will contribute
 * to some graphical representation such as a font.  The
 * set of possible keys is unbounded and can be anything.
 * Typically View implementations will respond to attribute
 * definitions and render something to represent the attributes.
 * <p>
 * Attributes can potentially resolve in a hierarchy.  If a
 * key doesn't resolve locally, and a resolving parent
 * exists, the key will be resolved through the parent.
 *
 * @author Timothy Prinzing
 * @see MutableAttributeSet
 */
public interface AttributeSet {

  /**
   * This interface is the type signature that is expected
   * to be present on any attribute key that contributes to
   * the determination of what font to use to render some
   * text.  This is not considered to be a closed set, the
   * definition can change across version of the platform and can
   * be amended by additional user added entries that
   * correspond to logical settings that are specific to
   * some type of content.
   */
  public interface FontAttribute {

  }

  /**
   * This interface is the type signature that is expected
   * to be present on any attribute key that contributes to
   * presentation of color.
   */
  public interface ColorAttribute {

  }

  /**
   * This interface is the type signature that is expected
   * to be present on any attribute key that contributes to
   * character level presentation.  This would be any attribute
   * that applies to a so-called <i>run</i> of
   * style.
   */
  public interface CharacterAttribute {

  }

  /**
   * This interface is the type signature that is expected
   * to be present on any attribute key that contributes to
   * the paragraph level presentation.
   */
  public interface ParagraphAttribute {

  }

  /**
   * Returns the number of attributes that are defined locally in this set.
   * Attributes that are defined in the parent set are not included.
   *
   * @return the number of attributes &gt;= 0
   */
  public int getAttributeCount();

  /**
   * Checks whether the named attribute has a value specified in
   * the set without resolving through another attribute
   * set.
   *
   * @param attrName the attribute name
   * @return true if the attribute has a value specified
   */
  public boolean isDefined(Object attrName);

  /**
   * Determines if the two attribute sets are equivalent.
   *
   * @param attr an attribute set
   * @return true if the sets are equivalent
   */
  public boolean isEqual(AttributeSet attr);

  /**
   * Returns an attribute set that is guaranteed not
   * to change over time.
   *
   * @return a copy of the attribute set
   */
  public AttributeSet copyAttributes();

  /**
   * Fetches the value of the given attribute. If the value is not found
   * locally, the search is continued upward through the resolving
   * parent (if one exists) until the value is either
   * found or there are no more parents.  If the value is not found,
   * null is returned.
   *
   * @param key the non-null key of the attribute binding
   * @return the value of the attribute, or {@code null} if not found
   */
  public Object getAttribute(Object key);

  /**
   * Returns an enumeration over the names of the attributes that are
   * defined locally in the set. Names of attributes defined in the
   * resolving parent, if any, are not included. The values of the
   * <code>Enumeration</code> may be anything and are not constrained to
   * a particular <code>Object</code> type.
   * <p>
   * This method never returns {@code null}. For a set with no attributes, it
   * returns an empty {@code Enumeration}.
   *
   * @return the names
   */
  public Enumeration<?> getAttributeNames();

  /**
   * Returns {@code true} if this set defines an attribute with the same
   * name and an equal value. If such an attribute is not found locally,
   * it is searched through in the resolving parent hierarchy.
   *
   * @param name the non-null attribute name
   * @param value the value
   * @return {@code true} if the set defines the attribute with an equal value, either locally or
   * through its resolving parent
   * @throws NullPointerException if either {@code name} or {@code value} is {@code null}
   */
  public boolean containsAttribute(Object name, Object value);

  /**
   * Returns {@code true} if this set defines all the attributes from the
   * given set with equal values. If an attribute is not found locally,
   * it is searched through in the resolving parent hierarchy.
   *
   * @param attributes the set of attributes to check against
   * @return {@code true} if this set defines all the attributes with equal values, either locally
   * or through its resolving parent
   * @throws NullPointerException if {@code attributes} is {@code null}
   */
  public boolean containsAttributes(AttributeSet attributes);

  /**
   * Gets the resolving parent.
   *
   * @return the parent
   */
  public AttributeSet getResolveParent();

  /**
   * Attribute name used to name the collection of
   * attributes.
   */
  public static final Object NameAttribute = StyleConstants.NameAttribute;

  /**
   * Attribute name used to identify the resolving parent
   * set of attributes, if one is defined.
   */
  public static final Object ResolveAttribute = StyleConstants.ResolveAttribute;

}
